The Impact of Intraocular Pressure Changes on Corneal Biomechanics in Primary Open-angle Glaucoma.

ABSTRACT

PURPOSE: To investigate the relationship between intraocular pressure (IOP) changes and corneal biomechanical properties, determine the quantitative relationship between IOP changes and corneal biomechanical properties in patients with glaucoma and observe the differences among different types of glaucoma when the effects of high-level IOP were excluded. DESIGN: Prospective clinical cohort study. METHODS: Setting: Institutional. PATIENTS Treatment-naive patients with primary open-angle glaucoma or ocular hypertension (OHT) were included. OBSERVATION PROCEDURES IOP was measured using a Goldmann applanation tonometer. Corneal biomechanics were evaluated using a corneal indentation device and corneal visualization Scheimpflug technology. Medication therapy was used for IOP reduction. Repeated measurements were taken at the baseline visit and each week thereafter within a month. Paired t tests were used to compare IOP and corneal biomechanical metrics before and after IOP-lowering therapy. One-way analysis of variance was employed to investigate potential differences across groups, with a Bonferroni post hoc correction administered for multiple intergroup comparisons. MAIN OUTCOME MEASURES: Corneal biomechanical parameters following IOP changes. RESULTS: Eighty-one participants (mean age, 41.63 ± 17.33 years) were included in this study. The cohort comprised 20 patients with normal-tension glaucoma (NTG), 47 with high-tension glaucoma (HTG), and 14 with OHT. The baseline corneal stiffness (88.58 ± 18.30 N/m) and corneal modulus (0.71 ± 0.16 MPa) were greater than the post-IOP reduction values (67.15 ± 9.24 N/m and 0.54 ± 0.08 MPa, respectively; P < .001). The relationships between changes in IOP and changes in corneal biomechanical parameters were Δ corneal stiffness = 2.06*ΔIOP+6.47 (P < .001) and Δ corneal modulus = 0.017*ΔIOP+0.051 (P < .001). After IOP reduction, the mean corneal stiffness at the 4th week in the NTG group was significantly lower (60.97 ± 6.36 N/m) than that in the HTG (67.25 ± 9.01 N/m) and OHT (75.62 ± 6.52 N/m, P < .001) groups. Additionally, the stiffness of HTG patients was lower than that of OHT patients (P = .003). CONCLUSIONS: Changes in IOP have an impact on corneal biomechanical parameters. Decreases in corneal stiffness and modulus were observed after IOP reduction. When the effect of high-level IOP was excluded, corneal biomechanics varied according to the type of glaucoma. The HTG corneas were softer than the OHT corneas, and the NTG corneas were even softer.